Overcoat and adhesive compositions based on chlorinated polyolefins having high chlorine contents

ABSTRACT

Adhesive compositions based on chlorinated polyolefins having chlorine contents greater than about 60 percent and molecular weights greater than about 500. The adhesive compositions contain the chlorinated polyolefin and a crosslinking agent. The chlorinated polyolefins are advantageous in that they can be prepared in an environmentally acceptable manner and can be utilized as a substitute for the traditional chlorinated natural rubber materials utilized in adhesive compositions without compromising adhesive performance. Preferred chlorinated polyolefins are prepared by a process involving the dispersion and chlorination of high surface area polyolefinic particles in an aqueous medium.

This application is a division of application Ser. No. 08/180,139, filedJan. 11, 1994, now U.S. Pat. No. 5,492,963.

FIELD OF THE INVENTION

The present invention relates to adhesive compositions useful forbonding various materials such as elastomeric materials to metalsubstrates. More specifically, the present invention relates to adhesivecompositions based on chlorinated polyolefins having significantly highchlorine contents.

BACKGROUND OF THE INVENTION

There is a wide variety of adhesive compositions currently available forbonding elastomeric materials to metal surfaces. Many of these adhesivecompositions utilize various halogenated polymers to provide theadhesive compositions with film-forming capability, enhanced adhesion,and resistance to adverse environmental conditions. One of the mostcommon and most effective halogenated polymeric materials is chlorinatednatural rubber or chlorinated synthetic rubber such as chlorinatedpolyisoprene. The chlorinated natural and synthetic rubbers have beenfound to provide excellent film-forming properties, adhesional affinityfor both metal surfaces and vulcanizing elastomers, and environmentalresistance when utilized in adhesive compositions for bondingelastomeric materials to metal surfaces.

The process for preparing the chlorinated rubber materials traditionallyemployed in adhesive compositions typically involves the utilization ofhighly chlorinated solvents such as carbon tetrachloride. The increasingnumber of environmental regulations relating to chlorinated solvents haslimited the availability and usability of many chlorinated solvents. Infact, the utilization of chlorinated solvents in industry may becometotally prohibited in the very near future.

Processes for preparing chlorinated rubber materials which do notutilize chlorinated solvents are therefore currently being explored.However, a process has yet to be developed which produces chlorinatedrubber materials equivalent to the materials produced by a process basedon chlorinated solvents such as carbon tetrachloride. Therefore, theadhesive industry is searching for alternative materials which can beprepared without the utilization of chlorinated solvents and which canact as an effective substitute for the traditional chlorinated rubbermaterials.

Chlorinated polyolefins, such as chlorinated polyethylene, can beprepared without the utilization of chlorinated solvents and havepreviously been considered for utilization in rubber-to-metal adhesivecompositions as alternatives to chlorinated rubber materials.Chlorinated polyolefins, however, have traditionally not providedadequate metal-wetting capability or environmental resistance so as tobe effective for use in rubber-to-metal adhesive compositions.

A need therefore exists for a chlorinated polymeric material which canbe prepared without the utilization of chlorinated solvents and whichcan be utilized as an effective substitute for the traditionalchlorinated rubber materials.

SUMMARY OF THE INVENTION

The present invention relates to chlorinated polyolefins which can beprepared without the utilization of chlorinated solvents and which canbe utilized in rubber-to-metal adhesive compositions so as to provideeffective metal-wetting capability, adhesional affinity for vulcanizingrubber, and environmental resistance. It has presently been unexpectedlydiscovered that chlorinated polyolefins having significantly highchlorine contents can be utilized in adhesive compositions so as toprovide performance equivalent to or greater than the performanceprovided by the traditional chlorinated rubber materials utilized inadhesive compositions. More specifically, the present invention relatesto an adhesive composition comprising a chlorinated polyolefin and acrosslinking agent wherein the chlorinated polyolefin has a chlorinecontent greater than about 60 percent and a molecular weight greaterthan about 500. The highly chlorinated polyolefins of the invention arepreferably prepared by a process involving the dispersion andchlorination of high surface area polyolefinic particles in an aqueousmedium.

DETAILED DESCRIPTION OF THE INVENTION

The polyolefin of the chlorinated polyolefin of the present inventioncan essentially be any polyolefin derived from ethylene and/or propylenemonomers. Typical examples of polyolefins that can be utilized toprepare the chlorinated polyolefins of the present invention includepolyethylene, polypropylene, ethylene-propylene copolymer,ethylene-propylene-diene terpolymer, ethylene-propylene-hexadieneterpolymer, ethylene-propylenedicyclopentadiene terpolymer,ethylene-propylene-ethylidenenorbornene terpolymer, with polyethylenebeing presently preferred.

The polyolefins of the invention may be chlorinated by techniques suchas dissolving or dispersing the polyolefin in a solvent or water andsubjecting the resulting solution to chlorine gas. Other chlorinationmethods suitable for preparing the chlorinated polyolefins of thepresent invention include directing chlorine gas into melted or moltenpolyolefin. Whatever method is utilized, it is essential that thechlorination be carried out until the chlorine content of the polyolefinis in the range from about 60 to 75 percent, preferably from about 65 to70 percent. The chlorinated polyolefins will typically have a molecularweight ranging from about 500 to 15,000, preferably from about 1,000 to7,000. A chlorinated polyolefin having the specific chlorine contentsand molecular weights described above will also typically have aviscosity in toluene at 20 weight percent and 25° C. of between about 10centipoise and 500 centipoise, preferably between about 100 centipoiseand 350 centipoise. As stated above, it is the significantly highchlorine content that has presently been found to cause the chlorinatedpolyolefins to exhibit the superior properties of the present invention.

A certain class of polyolefins has been found to be particularly usefulin adhesive compositions for purposes of the present invention. Thisclass of chlorinated polyolefins is prepared from environmentallyacceptable processes which do not involve the utilization of chlorinatedsolvents such as carbon tetrachloride. These environmentally acceptableprocesses have been found to readily produce chlorinated polyolefinshaving the significantly high chlorine contents required by the presentinvention. A number of these environmentally acceptable processes aredisclosed in, for example, Japanese Patent Application Nos. 4173808,4036302, 3199274, 3199206, 3199207, and 4046905 as well as in U.S. Pat.No. 5,180,791.

An exemplary environmentally acceptable process utilized to prepare thepreferred chlorinated polyolefins of the invention generally firstinvolves the formation of a suspension or dispersion of a finepolyolefin powder having a high surface area in water. The suspension ordispersion is typically stabilized by the use of a surfactant such asnon-ionic and/or anionic type surfactants. Examples of non-ionic typesurfactants include polyoxyalkylene condensates of long chain fattyacids or alcohols such as stearic acid or oleyl alcohol, or sorbitanderivatives of same, such as sorbitan monostearate and theircombinations, while examples of anionic type surfactants include longchain fatty acid soaps such as sodium stearate, alcohol sulfates, andrelated materials. A preferred anionic surfactant for preparing anaqueous suspension or dispersion of polyethylene powder is sodiumstearate.

The aqueous suspension or dispersion of the polyolefin is then typicallysubjected to chlorine gas in the presence of free-radical initiators orultraviolet irradiation. The chlorination is normally carried out in thetemperature range from about 0° C. to 70° C. The chlorination processmay be interrupted at a point where the polyolefin chlorine content isless than 55 percent and the dispersion then ball-milled or processedmechanically so as to expose the inner portion of each dispersedpolyolefin particle. This enables chlorination to proceed at a fasterrate than would be otherwise possible from that point. It is importantthat chlorination conditions be not so severe as to cause considerablechain scissioning of the polyolefin polymer chains. When the desiredchlorination level is reached, the chlorinated polyolefin may beseparated by filtration, washed with water, and dried under vacuum.

An example of a preferred environmentally acceptable process useful forpreparing the high chlorine content chlorinated polyethylenes of thepresent invention utilizes finely pulverized polyolefin powder having asurface area of from about 300 to 20,000 cm^(2/) g suspended in anaqueous medium and is described in detail in UK Patent Application No. 2239 457A and U.S. Pat. No. 5,180,791.

The chlorinated polyolefins are typically utilized in an amount rangingfrom about 5 to 95, preferably from about 25 to 70, percent by weight ofthe essential ingredients of the present invention. Essentialingredients of the present invention herein refers to the chlorinatedpolyolefin and the crosslinking agent.

The crosslinking agent of the invention can be essentially any compoundcapable of crosslinking the chlorinated polyolefins of the presentinvention. Examples of crosslinking agents useful in the presentinvention include aromatic nitroso compounds, aromatic dioximes andaliphatic bis-nitroamines with aromatic nitroso compounds beingpresently preferred.

The preferred aromatic nitroso compounds of the present invention can beany aromatic hydrocarbon, such as benzenes, naphthalenes, anthracenes,biphenyls, and the like, containing at least two nitroso groups attacheddirectly to non-adjacent ring carbon atoms. More particularly, suchnitroso compounds are described as aromatic compounds having from 1 to 3aromatic nuclei, including fused aromatic nuclei, having from 2 to 6nitroso groups attached directly to non-adjacent nuclear carbon atoms.The present preferred nitroso compounds are the dinitroso aromaticcompounds, especially the dinitrosobenzenes and dinitrosonaphthalenes,such as the meta- or para-dinitrosobenzenes and the meta- orpara-dinitrosonaphthalenes. The nuclear hydrogen atoms of the aromaticnucleus can be replaced by alkyl, alkoxy, cycloalkyl, aryl, aralkyl,alkaryl, arylamine, arylnitroso, amino, halogen, and like groups. Thepresence of such substituents on the aromatic nuclei has little effecton the activity of the nitroso compounds in the present invention. Asfar as is presently known, there is no limitation as to the character ofthe substituent, and such substituents can be organic or inorganic innature. Thus, where reference is made herein to nitroso compound, itwill be understood to include both substituted and unsubstituted nitrosocompounds, unless otherwise specified.

Particularly preferred nitroso compounds are characterized by theformula:

    (R)m--Ar--(NO).sub.2

wherein Ar is selected from the group consisting of phenylene andnaphthalene; R is a monovalent organic radical selected from the groupconsisting of alkyl, cycloalkyl, aryl, aralkyl, alkaryl, arylamine, andalkoxy radicals having from 1 to 20 carbon atoms, amino, or halogen, andis preferably an alkyl group having from 1 to 8 carbon atoms; and m iszero, 1, 2, 3, or 4, and preferably is zero.

A partial non-limiting listing of nitroso compounds which are suitablefor use in the practice of the invention include m-dinitrosobenzene,p-dinitrosobenzene, m-dinitrosonaphthalene, p-dinitrosonaphthalene,2,5-dinitroso-p-cymeme, 2-methyl-1,4-dinitrosobenzene,2-methyl-5-chloro-1,4-dinitrosobenzene, 2-fluoro- 1,4-dinitrosobenzene,2-methoxy- 1-3-dinitrosobenzene, 5-chloro-1,3-dinitrosobenzene,2-benzyl-1,4-dinitrosobenzene, 2-cyclohexyl-1,4-dinitrosobenzene andcombinations thereof. Particularly preferred nitroso compounds includep-dinitrosobenzene and m-dinitrosobenzene.

The crosslinking agent of the invention is typically utilized in anamount ranging from about 10 to 60, preferably about 30 to 40, percentby weight of the essential ingredients of the present invention.

In addition to the chlorinated polyolefin, the adhesive compositions ofthe present invention preferably contain an additional halogenatedpolymeric material which can function, in addition to the chlorinatedpolyolefin described above, as a film-forming component. The additionalhalogenated polymeric material may be essentially any halogenatedpolymer other than chlorinated polyolefins having the specific chlorinecontents and molecular weights described above, and representativeexamples include chlorinated natural rubber, chlorine- andbromine-containing synthetic rubbers including polychloroprene,chlorinated polychloroprene, chlorinated polybutadiene,butadiene/halogenated cyclic conjugated diene adducts, chlorinatedbutadiene styrene copolymers, chlorosulfonated polyethylene, brominatedpoly(2,3-dichloro-1,3-butadiene), copolymers of α-haloacrylonitriles and2,3-dichloro-1,3-butadiene, polyvinyl-butyral, chlorinated poly(vinylchloride), and mixtures thereof. Thus substantially any of the knownhalogen-containing derivatives of natural and synthetic elastomers canbe employed as additional halogenated polymeric materials in thepractice of this invention, including mixtures of such elastomers. It ispresently preferred to utilize brominatedpoly(2,3-dichloro-1,3-butadiene) and/or chlorosulfonated polyethylene asthe additional halogenated polymeric material of the invention.

If utilized, the additional halogenated polymeric material is typicallyemployed in an amount ranging from about 1 to 99, preferably from about10 to 40, percent by weight of the total ingredients (excluding waterand solvent) of the adhesive composition.

The adhesive compositions of the present invention may optionallycontain an acid-scavenging compound for purposes of consuming any acidcompound by-products produced during the bonding process. Theacid-scavenging compound of the present invention can be any known metaloxide such as the oxides of zinc, cadmium, magnesium, lead, andzirconium; litharge; zirconium salts; and combinations thereof. Variouslead-containing compounds may also be utilized as an acid-scavengingcompound in lieu of, or in addition to, the metal oxide. Examples ofsuch lead-containing compounds include lead salts such as polybasic leadsalts of phosphorous acid and saturated and unsaturated organicdicarboxylic acids and acid anhydrides. Specific examples of lead saltsinclude dibasic lead phthalate, monohydrous tribasic lead maleate,tetrabasic lead fumarate, dibasic lead phosphite, and mixtures thereof.Other examples of lead-containing compounds include basic leadcarbonate, lead oxide and lead dioxide. The acid-scavenging compound mayalso be an oxirane (epoxy) compound.

If utilized, the acid-scavenging compound is typically employed in anamount ranging from about 0.1 to 10, preferably from about 0.5 to 2,percent by weight of the total ingredients (excluding water and solvent)of the adhesive composition.

The adhesive compositions of the present invention can optionallycontain other well-known additives including plasticizers, fillers,pigments, surfactants, dispersing agents, wetting agents, reinforcingagents and the like, in amounts employed by those skilled in theadhesive arts to obtain a desired color and consistency. Examples ofoptional ingredients include carbon black, silica such as fumed silica,sodium aluminosilicate, and titanium dioxide and organic pigments ordyestuffs.

The adhesive compositions of the present invention may be prepared assolvent-based or water-based formulations. In the case of asolvent-based formulation, the ingredients of the adhesive are combinedin an appropriate solvent. The solvent may essentially be any solventcapable of adequately dissolving the ingredients for purposes of formingan adhesive composition capable of being applied as a thin film.Solvents useful for preparing formulations according to the presentinvention include aliphatic ketones, such as methylethyl ketone,methylisobutyl ketone, aliphatic esters such as ethylacetate and butylacetate, and aromatic hydrocarbons such as toluene and xylene. Thesolvent is typically utilized in an amount sufficient to obtain a totalsolids (non-volatile) content ranging from about 10 to 40, preferablyfrom about 20 to 30, percent.

In the case of water-based formulations, the chlorinated polyolefin isutilized in the form of a latex. The latex of the chlorinated polyolefinmay be prepared according to methods known in the art such as bydissolving the chlorinated polyolefin in a solvent and adding asurfactant to the resulting solution. Water can then be added to thesolution under high shear to emulsify the polymer. The solvent is thenstripped to obtain a latex which can be suitably utilized in awater-based formulation. The latex of the chlorinated polyolefin is thencombined with the other ingredients and a sufficient amount of water,preferably deionized water, so as to prepare an adhesive compositionhaving a typical total solids content of between about 10 and 70percent, preferably between about 30 and 50 percent.

The adhesive compositions may be applied to a surface to be bonded byspraying, dipping, brushing, wiping, roll-coating or the like, afterwhich the adhesive composition is permitted to dry. The adhesivecomposition is typically applied in an amount sufficient to form a dryfilm thickness ranging from about 0.1 to 1.0 mils, preferably from about0.2 to 0.8 mils.

The adhesive compositions of the present invention are capable ofbonding any substrate or surface capable of receiving the adhesivecomposition. The material, which may be bonded to a surface such as ametal surface in accordance with the present invention, is preferably apolymeric material, including any elastomeric material selected from anyof the natural rubbers and olefinic synthetic rubbers includingpolychloroprene, polybutadiene, neoprene, styrene-butadiene copolymerrubber, isobutylene-isoprene copolymer rubber, ethylene-propylene dieneterpolymer rubber, acrylonitrile-butadiene copolymer rubber, brominatedisobutylene-isoprene copolymer rubber, and the like. The surface towhich the material is bonded can be any surface capable of receiving theadhesive such as a glass, plastic, or fabric surface, and is preferablya metal surface selected from any of the common structural metals suchas iron, steel (including stainless steel), chemically treated steelsuch as zinc-phosphatized steel, lead, aluminum, chemically treatedaluminum such as anodized aluminum, copper, brass, bronze, Monel metal,nickel, zinc, and the like.

The present adhesive compositions are preferably utilized to bond anelastomeric material to a metal surface. The adhesive composition istypically applied to the metal surface and the coated metal surface andelastomeric substrate are then brought together under heat and pressureto complete the bonding procedure. The surface of the metal and theelastomeric substrate are typically brought together under a pressure offrom about 20.7 to 172.4 Mega Pascals (M Pa), preferably from about 20MPa to 50 MPa. The resulting rubber-metal assembly is simultaneouslyheated to a temperature of from about 130° C. to 220° C., preferablyfrom about 140° C. to 170° C. The assembly should remain under theapplied pressure and temperature for a period of from about 3 minutes to60 minutes, depending on the cure rate and thickness of the rubbersubstrate. This process may be carried out by applying the rubbersubstrate as a semi-molten material to the metal surface as in, forexample, an injection-molding process. The process may also be carriedout by utilizing compression molding, transfer molding or autoclavecuring techniques. After the process is complete, the bond is fullyvulcanized and ready for use in a final application.

The adhesive compositions of fie invention may be utilized in one- ortwo-coat adhesive systems. In a one-coat system, the adhesivecomposition is simply applied between the materials to be bonded. In atwo-coat system, the present adhesive composition is utilized as anadhesive overcoat which is typically applied to a metal surface whichhas first been primed with a conventional adhesive primer.

The following examples are provided for purposes of illustrating theinvention and are not intended to limit the scope of the presentinvention which is defined by the claims.

EXAMPLE 1

To a disperser is added 1,100 g of xylene and while running thedisperser, 90 g of carbon black, 60 g of dibasic lead phosphite, 5 g offumed silica, and 30 g of p-dinitrosobenzene are added in this order.The temperature of the resulting p-dinitrosobenzene dispersion is keptbelow 60° C., and the disperser is stopped when the fineness, asmeasured with a HAGEMAN grind gauge, reaches 1.5 mils or less. To ablending vessel equipped with a stirrer is then added 1,400 g of xylene.The stirrer is started and 600 g of chlorinated polyethylene (CPE-HE1200-Nippon Paper Industries) having a viscosity in 20 percent by weighttoluene solution at 25° C. of 350 cps and a chlorine content of 67percent, is added to the blending vessel and dissolved to form achlorinated polyethylene solution. The above p-dinitrosobenzenedispersion and 200 g of 30 percent by weight brominatedpoly-2,3-dichlorobutadiene (23 percent bromine content)perchloroethylene solution are added to the chlorinated polyethylenesolution in this order and the blend is stirred for 1 hour.

EXAMPLE 2

An adhesive is prepared by the same procedure as in Example 1, exceptthat the viscosity and chlorine content of the chlorinated polyethyleneemployed are 70 cps and 68 percent, respectively.

Comparative Example 3

An adhesive is prepared by the same procedure as in Example 1, exceptthat chlorinated natural rubber (ADK CR-701-Asahi Denka Kogyo K.K.) isemployed in place of the chlorinated polyethylene. The viscosity andchlorine content of the chlorinated natural rubber are 169 cps and 67percent, respectively.

The adhesive compositions prepared above in Examples 1-3 are coated ontogrit-blasted, degreased 1.6 mm×25 mm×60 mm steel coupons by dipping thecoupons in the adhesive compositions. The coated coupons are allowed todry for approximately one hour at ambient conditions.

The coated coupons are bonded to natural rubber (NR),isobutylene-isoprene copolymer rubber (IIR), and styrene-butadienecopolymer rubber (SBR). The rubber is bonded to the coated coupons bycompression molding at a pressure of 100 kg ft./cm². The bondingtemperatures and times for the NR, IIR, and SBR substrates are 154° C.,160° C. and 154° C.; and 5 minutes, 30 minutes, and 30 minutes,respectively. Some of the coated coupons are exposed to pre-bake orpre-cure heat conditions. When pre-baked, the coupons are exposed to atemperature of 154° C. for 5 minutes. This simulates actual productionconditions and helps determine if the adhesive remains active enough tosuccessfully bond the rubber compound. The bonded rubber-metalassemblies are then subjected to the following tests.

Initial Adhesion

Bonded parts are pulled to destruction according to ASTM Test D429 -Method B. Parts are tested in peel with a peel angle of 45 degrees. Thetest is conducted at room temperature with a test speed of 20 inches perminute. After the bonded part fails, the peak peel strength value(measured in kg/in.) and the percent rubber retention on the adhesivecoated area of the part are measured.

Two-Hour Boiling Water

Bonded parts are buffed on the edges with a grinding wheel. The rubberis then tied back over the metal with stainless steel wire so as tostress the bonded area. This exposes the bond line to the environment.Failure is initiated by scoring the bond line with a razor blade. Theparts are then placed in a beaker filled with boiling tap water. Theparts remain in this environment for 2 hours. The peel strength andpercent rubber retention on the part are then measured.

The results of the above tests are set forth in Table 1 below. In thedata, reference is made to failure in the rubber body (R). Failure isexpressed in terms of percent, and a high percent of failure in therubber is desirable since this indicates that the adhesive bond isstronger than the rubber itself. The indication X/YR means that theadhesive exhibited a peel strength of X kg/in. and a rubber failure of Ypercent.

                  TABLE 1                                                         ______________________________________                                        Substrate                                                                             Test       Ex. 1     Ex. 2   Ex. 3                                    ______________________________________                                        NR      Initial     32.8/100 R                                                                             13.3/2 R                                                                               25.8/100 R                                      Boiling water                                                                            36.2/99 R 16.9/6 R                                                                              28.2/96 R                                        Initial.sup.(a)                                                                          13.6/40 R 7.2/0 R 8.6/0 R                                  IIR     Initial    47.2/99 R 48.8/98 R                                                                             43.6/66R                                 SBR     Initial     83.5/100 R                                                                             88.0/97 R                                                                             63.5/98 R                                ______________________________________                                         .sup.(a) Subjected to prebake of 154° C. for 5 minutes.           

EXAMPLE 4

To a disperser is added 122 g of xylene and while running the disperser,10 g of carbon black, 5.0 g of dibasic lead phosphite, and 28 g ofp-dinitrosobenzene pre-dispersed in xylene (at 37.2% non-volatilecontent) are added in this order. The temperature of the dispersion iskept below 60° C. and the dispersion is continued until the fineness ofthe dispersion as measured with a HAGEMAN grind gauge reaches 1.5 milsor less. Then 10 g of chlorinated polyethylene (CPE-HE 1200 - NipponPaper Industries) having a viscosity in 20 percent by weight toluenesolution at 25° C. of 350 cps and a chlorine content of 67 percentchlorinated polyethylene is added to the dispersion and mixing iscontinued until the chlorinated polyethylene dissolves to form anintermediate dispersion.

To a blending vessel equipped with a stirrer is added 84.5 g of xylene.Then an additional 50 g of the chlorinated polyethylene is added to theblending vessel under agitation along with 175 g of the aboveintermediate dispersion. To the resulting mixture is then added 125 g ofa 12.0 percent solution in toluene of chlorosulfonated polyethylene(HYPALON 45-E. I. Du Pont de Nemours & Co.), and 85.5 g of brominatedpoly-2,3-dichlorobutadiene (23 percent bromine content) solution inperchloroethylene at 29.2 percent non-volatile content.

The final formulation, comprising 60 g total of chlorinatedpolyethylene, 25 g of brominated poly-2,3-dichlorobutadiene, 15 g ofchlorosulfonated polyethylene, 10 g of p-dinitrosobenzene, 10 g ofcarbon black, and 5.0 g of dibasic lead phosphate as its non-volatileingredients, has an overall non-volatile content of 24.0 percent.

Comparative Example 5

An adhesive composition is prepared according to Example 4 except thatthe intermediate dispersion comprises 123.1 g of xylene, 10 g of carbonblack, 5.0 g of dibasic lead phosphite, 26.9 g of p-dinitrosobenzene(itself predispersed in xylene at 37.2 percent non-volatile content),and 10 g of the same chlorinated natural rubber as used in Example 3.

The final formulation, comprising 70 g total of chlorinated naturalrubber, 30 g of brominated polydichlorobutadiene, 10 g ofp-dinitrosobenzene, 10 g of carbon black, and 5.0 g of dibasic leadphosphate as its nonvolatile ingredients, also has an overallnon-volatile content of 24.0 percent.

Grit blasted steel coupons that have also been solvent degreased aredip-coated with a conventional primer (CHEMLOK 205-Lord Corporation),dried, and then dip-coated with the two overcoat adhesives of Examples 4and 5. The coated coupons are bonded to 1/4" thick pads of a standardformulation of natural rubber by placing them in a compression mold for15 minutes at 154° C. They are tested for initial bond strength andpercent rubber failure, and also for percent rubber failure after beingstressed and exposed to boiling water for 3 hours. The results are shownbelow in Table 2.

                  TABLE 2                                                         ______________________________________                                        Substrate  Test        Ex. 4    Ex. 5                                         ______________________________________                                        NR         Initial     30/100 R 27/100 R                                                 Boiling water                                                                               100 R    100 R                                       ______________________________________                                    

EXAMPLE 6

To a vessel equipped with a stirrer is added 1200 g of xylene. Thestirrer is started and 150 g of chlorosulfonated polyethylene (HYPALON40 E. I. Du Pont de Nemours & Co.) with a chlorine content of 36 percentby weight is added and dissolved to form an intermediate solution.

To a disperser is added 510 g of xylene. While running the disperser, 45g of carbon black, 100 g of dibasic lead phosphite, and 90 g ofp-dinitrosobenzene are added in this order. The temperature of thedispersion is kept below 60° C. When the fineness, as measured with aHAGEMAN grind gauge, reaches 1.5 mils or less, 100 g of the aboveintermediate solution of chorosulfonated polyethylene is added to thedispersion.

The disperser is stopped when the fineness reaches 1.5 mils or less.Then the dispersion, 45 g of chlorinated polyethylene (CPE-HE 1200-Nippon Paper Industries) with viscosity of 20 percent by weight toluenesolution at 25° C. and chlorine content of 170 cps and 69 percentrespectively, and 200 g of chlorinated paraffin as a plasticizer areadded to the remaining chlorosulfonated polyethylene solution and theblend is stirred for 1 hour.

EXAMPLE 7

An adhesive is prepared by the same procedure as Example 6, but theviscosity and chlorine content of the chlorinated polyethylene employedare 180 cps and 69 percent respectively.

EXAMPLE 8

An adhesive is prepared by the same procedure as Example 6, except thatthe chlorinated natural rubber of Example 3 is employed in place of thechlorinated polyethylene.

Bonding and test methods employed for these adhesives are the same asExample 3 except that a conventional primer (CHEMLOK 205-LordCorporation) is applied at a dry film thickness of approximately 0.3mils to the test coupons and dried before applying these adhesives. Thebonding temperature and time for the ethylene-propylene-diene terpolymerrubber substrate (EPDM) are 160° C. and 30 minutes. The test results areshown below in Table 3.

                                      TABLE 3                                     __________________________________________________________________________    Rubber                                                                        Compound                                                                             Test Items                                                                            Ex. 6   Ex. 7   Ex. 8                                          __________________________________________________________________________    NR     Initial 29.0 - 100% R                                                                         29.1 - 100% R                                                                         29.3 - 100% R                                         Boiling Water                                                                         34.3 - 97% R                                                                          34.0 - 90% R                                                                          33.1 - 95% R                                          Initial.sup.(a)                                                                       29.5 - 97% R                                                                          30.3 - 98% R                                                                          30.5 - 97% R                                   IIR    Initial 49.8 - 100% R                                                                         51.1 - 100% R                                                                         51.0 - 100% R                                         Boiling Water                                                                         51.5 - 99% R                                                                          50.3 - 99% R                                                                          51.3 - 99% R                                          Initial.sup.(a)                                                                       48.5 - 98% R                                                                          47.3 - 98% R                                                                          46.8 - 100% R                                  SBR    Initial 75.1 - 100% R                                                                         75.8 - 100% R                                                                         74.8 - 100% R                                         Boiling Water                                                                         80.6 - 99% R                                                                          81.6 - 99% R                                                                          81.3 - 98% R                                          Initial.sup.(a)                                                                       73.1 - 100% R                                                                         75.0 - 100% R                                                                         75.5 - 100% R                                  EPDM   Initial 30.1 - 30% R                                                                          30.1 - 32% R                                                                          21.1 - 3% R                                           Boiling Water                                                                         28.0 - 32% R                                                                          29.3 - 35% R                                                                          21.5 - 9% R                                           Initial.sup.(a)                                                                       15.0 - 0% R                                                                           14.8 - 0% R                                                                           15.0% R                                        __________________________________________________________________________     .sup.(a) Subjected to prebake for 20 minutes at 150° C.           

As can be seen from the above data, the chlorinated polyolefins of thepresent invention provide adhesive performance equivalent to or greaterthan that provided by traditional chlorinated rubber materials.

What is claimed is:
 1. An adhesive composition comprising a firstchlorinated polyolefin, a crosslinking agent for said chlorinatedpolyolefin, and a second halogenated polymeric material, wherein thechlorinated polyolefin has a chlorine content greater than about 60percent and a molecular weight greater than about
 500. 2. An adhesivecomposition according to claim 1 wherein the second halogenatedpolymeric material is selected from the group consisting of chlorinatednatural rubber, chlorine- and bromine-containing synthetic rubbersincluding polychloroprene, chlorinated polychloroprene, chlorinatedpolybutadiene, butadiene/halogenated cyclic conjugated diene adducts,chlorinated butadiene styrene copolymers, chlorosulfonated polyethylene,brominated poly(2,3-dichloro-1,3-butadiene), copolymers ofα-haloacrylonitriles and 2,3-dichloro-1,3-butadiene, polyvinylbutyral,chlorinated poly(vinyl chloride), and mixtures thereof.
 3. An adhesivecomposition according to claim 2 wherein the second halogenatedpolymeric material is brominated poly(2,3-dichloro-1,3-butadiene),chlorosulfonated polyethylene or a combination thereof.